1. Field of the Invention
The invention relates generally to pipe couplings and more particularly to a system and method for retaining seal rings against a pipe flange to facilitate making and breaking of a pipe coupling.
2. Description of Related Art
The use of pipelines for handling fluids is widely known. High-volume pipelines are commonly used to carry oil, gas and other fluid hydrocarbons. High-pressure or high-temperature pipelines are commonly used in industrial applications. Pipelines may also be designed for many other purposes, such as carrying corrosive, toxic or otherwise dangerous fluids.
The pipelines used in these applications typically consist of a number of pipe sections which are connected end-to-end to form a single conduit. Typically, the pipe sections are joined by means of couplings or connectors which consist of a set of flanges attached to the ends of the pipe sections. The flanges are bolted or held together in some other manner to form a continuous conduit.
Is important to ensure that the couplings between pipe sections form tight seals. This is particularly true in systems which are designed to handle dangerous fluids (e.g., those which are operated at high pressures or high temperatures, or those which carry dangerous fluids.) Pipe couplings therefore normally include a gasket or some other type of seal located between the flanges of the couplings to provide a good seal.
In many heavy-duty, industrial systems such as oil transport pipelines, the pipelines may be very large and may have very thick walls which are designed to withstand tremendous pressures. For example, the pipe sections may be tens of inches in diameter and may have walls several inches thick. An example of a standard API coupling is illustrated in FIGS. 1a and 1b. FIG. 1a shows the disassembled flanges and seal ring, while FIG. 1b shows the assembled coupling. The seal rings used in the couplings must likewise be designed to withstand the high pressures and are often constructed of metal rather than a more elastic, but weaker and less durable material.
Because of their size, oil pipelines are heavy and unwieldy and are therefore difficult to construct and maintain. Although the flanges which are used in pipe couplings, such as standard ANSI and API flanges, are very simple in design, the size and weight of the components can make them difficult and dangerous with which to work. The danger and difficulty of working with these pipelines is often compounded by having to work in harsh environments. For example, many oil pipelines are installed in sub-sea environments, where vision may be severely limited, where movement may be difficult and where, if equipment is mishandled and dropped, it may fall to the sea floor and be unrecoverable.
One particular problem concerns the seal rings used in the couplings. As shown in FIGS. 1a and 1b, the seal ring simply sits in a groove (the seal seat) without being held in position. Consequently, the seal ring may easily be moved out of its seated position. If the coupling is assembled with the seal ring out of position, it may be damaged and may not provide a good seal. If the flange faces are vertically oriented, the seal ring may simply fall out of place. It is not unusual for the seal ring of a standard ANSI coupling to be improperly seated, damaged, or even lost when a worker is attempting to bolt up the coupling or to unbolt and break the coupling.
The present invention is intended to simplify the assembling or disassembling (xe2x80x9cmakingxe2x80x9d or xe2x80x9cbreakingxe2x80x9d) of a coupling by providing a retaining system for retaining a seal ring on one side of the coupling. Once the seal ring is placed in the proper position against one of the flanges of the coupling, the retaining system is used to hold it in that position. The seal ring secured by the retaining system cannot be moved out of position and therefore will not be damaged when the coupling is assembled. Further, the seal ring cannot fall out of place and cannot be lost when the coupling is disassembled. The present system and method thereby reduce the cost and effort related to assembly, disassembly and maintenance of pipe couplings.
One embodiment of the invention comprises a seal retaining system for retaining a seal ring in a pipe coupling, wherein a plurality of seal ring retainers are connected to a flange around the periphery of a seal seat and wherein the retainers can be moved from an open position in which a seal ring can be placed on or removed from the seal seat to a closed position in which the seal ring is retained in position on the seal seat. In this embodiment, each retainer comprises a rotatable cam having a lip which extends generally around the circumference of the cam, but is truncated on one side. When the truncated portion faces the seal seat, the seal ring can be installed or removed. When the truncated portion faces away from the seal seat, the seal ring is held in position on the seal seat. The cams may be attached with bolts that can be sheared off if the cams are frozen in position.
In one embodiment, a retaining system is implemented in a coupling having tapered, mating flanges and a tapered seal ring. In this type of coupling, a tight seal is provided by tapered male and female surfaces which are drawn together to compress the tapered seal ring therebetween. Because the seal is effected by the tapered surfaces, a gap can be allowed to remain between the planar surfaces of the flanges (standard flanges generally have no such gap.) A series of rotatable cams are placed generally around the circumference of the tapered surface on one of the flanges, where they can be positioned to extend over the edge of the seal ring and retain it in position against the flange. When the cams are rotated away from the seal ring, it can be removed from its position against the flange.
One embodiment comprises a method for assembling and/or disassembling a coupling which incorporates a seal ring retaining system as described herein. A first flange incorporating a plurality of cams is provided. The cams are located around a seating face of the flange and each cam is attached to the flange by a screw which is screwed into a corresponding threaded hole in the face of the flange. Each cam is loosened, if necessary, and rotated to an open position in which the cam does not extend over the position of a seal ring on the seating face. The seal ring is placed on the seating face, and the cams are rotated to their closed positions, in which part of each cam extends over part of the seal ring. The cams thereby prevent the seal ring from being removed from its position against the seating face of the first flange. The first flange is then placed in position against a second flange, with the seal ring contacting and forming a seal between the two flanges. The flanges are then secured together to form a sealed coupling.
When it is desired to disassemble the coupling, the bolts or other means which secured the flanges together are loosened and/or removed. The flanges are then separated, with the seal ring being retained on the first flange. The seal ring can be removed from the first flange by loosening each of the screws which attach the cams to the flange and rotating the cams to their open positions. If the screws cannot be loosened, the screws can be sheared off with a chisel or other tool. The screws can be shared off without damaging the seal ring or the seating face. When the cams are in their open positions or have been removed by shearing off the attachment screws, the seal ring can be a removed from its position on the seating face of the flange. If desired, a new seal ring can be seated on the flange and secured by the retaining system. Even if one or more of the cams have been removed (e.g., by shearing off their attachment screws,) it may be possible to secure the new seal ring with the remaining cams.